Recently, demand for secondary batteries such as lithium batteries, lithium ion batteries, and lithium ion polymer batteries is greatly increasing. The secondary battery is a rechargeable battery using an electrode material having excellent reversibility and the secondary battery may be a nickel-hydrogen (Ni-MH) battery, a lithium battery or a lithium ion battery depending on the anode and the cathode active material. Such secondary batteries are increasingly widely being applied to various applications as power supply sources for information technology (IT) devices such as smart phones, portable computers, and electronic paper, or for transportation systems such as electric vehicles.
A carbon-based material having a theoretical capacity of 372 mAh/g is generally applied as a material capable of inhibiting dendrites of lithium in a lithium battery from growing. However, as the application of the secondary battery has expanded, there has been a demand for higher capacity and higher output of the secondary battery than before. Accordingly, a non-carbon anode material capable of being alloyed with lithium such as silicon (Si), tin (Sn), or aluminum (Al) having a capacity of 500 mAh/g or more to replace the theoretical capacity of the carbon-based anode materials have greatly drawn attention.
Among the non-carbon-based anode materials, the silicon has the theoretical capacity of about 4,200 mAh/g, which is the largest. However, since the volume of the silicon anode material expands by about 4 times during charging of the silicon anode material, due to the volume change during charging and discharging, the electrical connection between the active materials may be broken, the active material may be separated from a current collector, and the active material may be eroded by electrolyte, which are a barrier to its practical use. Therefore, for the application of the silicon material to the anode material, it is required to improve the irreversibility of the battery due to the volume change during charging and discharging of the battery. In addition, with explosive growth of demand for secondary batteries, it is necessary to secure fabrication technology that can economically and mass-produce silicon anode active materials.